System and method for increasing upstream communication efficiency in an optical network

ABSTRACT

An optical transmitter of a subscriber optical interface and an optical receiver of a laser transceiver node can be designed to a frequency of data that is formatted according to a predetermined network protocol, that is encoded with a predetermined coding scheme, and that is transmitted according to a predetermined data transmit timing scheme. The frequency of data is an occupied frequency of a protocol when the data comprises a maximum number of like bits permitted by the protocol. An optical transmitter and optical receiver can be designed to a lowest occupied frequency of data that is encoded with 8B/10B encoding, and that is propagated upstream according to time division multiple access (TDMA). In this way, upstream optical communications can be maximized for speed.

PRIORITY CLAIM TO PROVISIONAL AND NON-PROVISIONAL APPLICATIONS

[0001] The present application is a continuation-in-part ofnon-provisional patent application entitled “System and Method forCommunicating Optical Signals between a Data Service Provider andSubscribers,” filed on Jul. 5, 2001 and assigned U.S. application Ser.No. 09/899,410. The present application also claims priority toprovisional patent application entitled, “Method for Decreasing theTransition Time of TDMA Systems” filed on Aug. 28, 2001 and assignedU.S. application Ser. No. 60/315,555. The entire contents of both thenon-provisional patent application and the provisional patentapplication mentioned above are hereby incorporated by reference.

TECHNICAL FIELD

[0002] The present invention relates to video, voice, and datacommunications. More particularly, the present invention relates toincreasing the speed and efficiency of upstream communications between adata service hub and a subscriber optical interface.

BACKGROUND OF THE INVENTION

[0003] The increasing reliance on communication networks to transmitmore complex data, such as voice and video traffic, is causing a veryhigh demand for bandwidth. To resolve this demand for bandwidth,communication networks are relying more upon optical fibers to transmitthis complex data. Conventional communication architectures that employcoaxial cables are slowly being replaced with communication networksthat comprise only fiber optic cables. One advantage that optical fibershave over coaxial cables is that a much greater amount of informationcan be carried on an optical fiber.

[0004] This need for increased data transfer rates is fueled by thevarious types of applications being supported by both optical networkarchitectures and the computers that are connected to them. Applicationsrequiring increased bandwidth and data transfer rates include scientificmodeling, engineering, publications, medical data transfer, datawarehousing, network back-up applications, desktop video conferencing,and interactive whiteboarding.

[0005] Many of these applications require the transmission of largefiles over a network. File sizes can include hundreds of megabytes togigabytes. Scientific applications demand ultra-high bandwidth networksto communicate three dimensional visualizations of complex objectsranging from chemical structures to engineering drawings. Magazines,brochures and other complex, full-color publications prepared on desktopcomputers employ optical networks to transmit data directly todigital-input printing facilities.

[0006] Many medical facilities are transmitting complex images overlocal area networks and wide area networks, enabling the sharing ofexpensive equipment in specialized medical expertise. Engineers areusing electronic and mechanical design automation tools to workinteractively and distributed development teams, sharing files in thehundreds of gigabytes. Data warehouses may comprise gigabytes orterabytes of data distributed over hundreds of platforms and accessed bythousands of users, and must be updated regularly to provide usersnear-real time data for critical business reports and analysis.

[0007] To address the enormous bandwidth concerns of the aforementionedapplications, point to multipoint optical networks architectures havebeen contemplated. With such optical network architectures, datatransfer upstream from the multipoints to the point often requires theuse of predetermined timing schemes, such as time division multipleaccess (TDMA).

[0008] Under the predetermined timing scheme of TDMA, multiple datasources must start and stop transmitting data rather quickly during apredefined interval. With conventional optical transmitters, a certainamount of time within any TDMA scheme must be allocated to allow anoptical transmitter to power up to an operating level for datatransmission and then to power down at the end of a data transmission.Further, additional time must be allocated in any TDMA scheme forallowing an optical receiver to adjust itself when receiving differentsignals from optical transmitters that may have different properties(such as signal strength, noise, and other factors).

[0009] This allocation of transition times within any TDMA timing schemedecreases efficiency of data transfer, due to reduction of the rate atwhich data is transferred from multipoints to a single point in anupstream direction. The aforementioned problems are linked to thehardware supporting the optical communications. This hardware is neededto support a very popular and conventional broadband networking standardreferred to as the synchronous optical network (SONET). A standardsimilar to SONET is referred to as the synchronous digital hierarchy(SDH) outside of the United States.

[0010] The majority of optical transmitters and receivers are designedto propagate data that is formatted according to the SONET transmissionstandard. One of the problems associated with the SONET transmissionstandard that accentuates or magnifies the limitations of currentconventional optical transmitters and receivers is that the minimumfrequency content of data formatted according to the SONET standard canextend to very close to zero by virtue of the SONET standard permittingthe transmission of up to 72 or more bits of the same type (the 1 or 0).

[0011] In other words, the SONET transmission standard could potentiallyformat data such that a string of 72 or more bits could be propagatedthat does not have a change in state. Such a transmission state ofidentical or similar bits requires the optical transmitters and theoptical receivers to be designed at very low frequencies compared to orrelative to other network protocols.

[0012] Another problem and drawback of conventional optical transmittersand optical receivers is that such equipment can have costs thatapproach (at the time of the writing of this text) of upward of hundredsof thousands of dollars. Accordingly, in light of the problemsidentified above with respect to conventional network protocols andconventional optical equipment, there is a need in the art for a methodand system for efficient propagation of data and broadcast signals overan optical network. There is a need in the art for a method and systemthat can increase the speed in which optical transmitters and opticalreceivers can handle data in an upstream direction relative to asubscriber and a data service hub. Specifically, a need exists in theart for a method and system that can increase the speed at which data istransmitted from multiple points to a single point, by reducing wastedtime spent switching transmission from one point to another.

[0013] A further need exists in the art for optical receivers that haveincreased speed to switch from receiving signals from one opticaltransmitter to another optical transmitter. And lastly, there is a needin the art to provide optical network equipment that can support anoptical network protocol at a substantially reduced cost compared to theequipment needed to operate conventional network protocols such asSONET.

SUMMARY OF THE INVENTION

[0014] The present invention is generally drawn to a system and methodfor efficient propagation of data and broadcast signals over an opticalnetwork. More specifically, the present invention is generally drawn toa method and system that increases the speed in which opticaltransmitters and optical receivers can handle data in an upstreamdirection relative to a subscriber and a data service hub.

[0015] According to one exemplary aspect of the present invention, anoptical network architecture can include a laser transceiver node and asubscriber optical interface. The laser transceiver node can comprise anoptical receiver that can convert upstream optical signals received fromthe subscriber optical interface into upstream electrical signalsdestined for a data service hub. Meanwhile, the subscriber opticalinterface can comprise an optical transmitter such as a laser operatingaccording to a predetermined timing scheme that produces the upstreamoptical signals received by the optical receiver housed in the lasertransceiver node.

[0016] Both the optical transmitter of the subscriber optical interfaceand the optical receiver of the laser transceiver node can handle afrequency of data that is formatted according to a predetermined networkprotocol that is encoded with a predetermined coding scheme, and that istransmitted according to a predetermined data transmit timing scheme.

[0017] A frequency of the data transmitted according to thepredetermined protocol can comprise an occupied frequency of a protocolthat is defined as the lowest frequency of a frequency spectrum when thedata comprises a maximum number of like bits permitted by thepredetermined network protocol. The optical transmitter and opticalreceiver can have time constants that are adjusted according to thislowest occupied frequency of data when data is formatted according tothe predetermined network protocol that can comprise Gigabit Ethernet(part of the IEEE 802.3 standard), that is encoded with 8B/10B encoding,and that is propagated upstream according to time division multipleaccess (TDMA).

[0018] In other words, the high frequency circuits present in theoptical transmitter and optical receiver can have time constants thatcan be adjusted for maximum efficiency when supporting data formattedaccording to the predetermined network protocol comprising GigabitEthernet with 8B/10B encoding and that is transmitted according to TDMA.

[0019] Similarly, the time constant of a power level circuit of eachoptical transmitter can be adjusted to increase the speed to power up alaser that generates the optical signals corresponding to the data.Other high frequency circuits of each optical receiver can have timeconstants that are adjusted to maximize efficiency for receiving thepredetermined network protocol comprising Gigabit Ethernet with 8B/10Bencoding according to a predetermined timing scheme. Other highfrequency circuits can include, but are not limited to, an opticaldetector circuit, an optional automatic gain control circuit, and alimiting/conversion circuit.

[0020] Specifically, the optical receiver of the laser transceiver nodecan be optimized for maximum efficiency when handling upstream dataformatted according to Gigabit Ethernet with 8B/10B encoding and apredetermined timing scheme such as TDMA. When the optical receiver'shigh frequency circuits have time constants that are adjusted to aspecific frequency or range of frequencies, the device can rapidlyswitch from receiving signals from one optical transmitter to another.In other words, the optical receiver can make necessary adjustments suchas gain control more quickly when receiving optical signals fromdifferent optical transmitters.

[0021] The quality of received optical signals generated by each opticaltransmitter can vary because of the different relative distances theoptical signals are transmitted over an optical network. Other factorsthat can cause optical signals generated by one transmitter to bedifferent from another transmitter can include laser power variation,optical component loss variation, and other similar factors known in theart. Further, an optical transmitter usually does not transmit readabledata when the transmitter first starts transmitting. The opticalreceiver usually needs to make adjustments to compensate for thedifferences in the optical signals in order to accurately convert theoptical signals into the electrical domain.

[0022] For each high frequency circuit mentioned above, adjusting of thetime constant can comprise adjusting capacitance values to correspond tothe frequency of data propagated according to the predetermined networkprotocol comprising Gigabit Ethernet with 8B/10B encoding and apredetermined timing scheme such as TDMA, according to one exemplaryembodiment. This usually means that the high pass time constants of eachhigh frequency circuit can be set lower than time constants designed tohandle data formatted according to different conventional protocols suchas SONET.

[0023] The lower time constants achieved according to the presentinvention generally correspond with data formatted according to apredetermined network protocol comprising Gigabit Ethernet with 8B/10Bencoding and TDMA. However, other network protocols, encoding, and datatransmit timing schemes for propagating data are not beyond the scope ofthe present invention. For example, other network protocols can include,but are not limited to, Fiber Distributed Data Interface (FDDI) andDigital Video Broadcasting-Asynchronous Serial Interface (DVB-ASI).Other encoding schemes can include, but are not limited to, 16B/18B and64B/66B encoding. Meanwhile, other data transmit timing schemes caninclude, but are not limited to, time division multiplexing (TDM) orcode division multiple access (CDMA).

[0024] By adjusting the time constants mentioned above, the presentinvention can increase the operating speeds for both the opticaltransmitter housed in the subscriber optical interface and the opticalreceiver housed in the laser transceiver node. Specifically, when thetime constants of the optical transmitter are adjusted, datatransmission can be increased since the delays normally attributed tostart-up and power down times for the optical transmitter can besignificantly reduced. This start up and power down time reduction foran optical transmitter can substantially improve data transmission rateswhen optical transmitters share bandwidth according to data transmittiming schemes such as time division multiple access (TDMA).

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a functional block diagram of some core components of anexemplary optical network architecture according to the presentinvention.

[0026]FIG. 2 is a functional block diagram illustrating an exemplaryoptical network architecture for the present invention.

[0027]FIG. 3 is a functional block diagram illustrating an exemplarydata service hub of the present invention.

[0028]FIG. 4 is a functional block diagram illustrating an exemplaryoutdoor laser transceiver node according to the present invention.

[0029]FIG. 5 is a functional block diagram illustrating an optical tapconnected to a subscriber interface by a single optical waveguideaccording to one exemplary embodiment of the present invention.

[0030]FIG. 6 is a functional block diagram illustrating upstream anddownstream communications in their respective timing schemes between thelaser transceiver node and the subscriber optical interface according toan exemplary embodiment of the present invention.

[0031]FIG. 7 is a functional block diagram illustrating an exemplarypredetermined timing scheme for upstream communications according to oneexemplary embodiment of the present invention.

[0032]FIG. 8 is a graph illustrating the amplitude versus the frequencyof data prorogated according to conventional optical protocols and anexemplary optical protocol according to the present invention.

[0033]FIG. 9 is a functional block diagram of some core components of adigital optical transmitter according to one exemplary embodiment of thepresent invention.

[0034]FIG. 10 is a functional block diagram illustrating some exemplarycomponents of a driver circuit of a digital optical transmitteraccording to one exemplary embodiment of the present invention.

[0035]FIG. 11 is an electrical circuit diagram of an exemplary digitaloptical transmitter according to one exemplary embodiment of the presentinvention.

[0036]FIG. 12 is a functional block diagram illustrating an exemplaryoptical receiver according to one exemplary embodiment of the presentinvention.

[0037]FIG. 13 is an electrical circuit diagram of an exemplary opticalreceiver according to the present invention.

[0038]FIG. 14 is a logic flow diagram illustrating an exemplary methodfor increasing upstream communication speed and optical network from avantage point of an optical transmitter according to one exemplaryembodiment of the present invention.

[0039]FIG. 15 is a logic flow diagram illustrating an exemplarysubprocess for increasing speed to convert electrical data to serialdata according to one exemplary embodiment of the present invention.

[0040]FIG. 16 is a logic flow diagram illustrating an exemplarysubprocess for increasing speed to convert serial encoded data into theoptical domain.

[0041]FIG. 17 is a logic flow diagram illustrating a subprocess forincreasing speed to power up a laser for optical transmissions accordingto one exemplary embodiment of the present invention.

[0042]FIG. 18 is a logic flow diagram illustrating an exemplary methodfor increasing upstream communication speed in an optical network fromthe vantage point of an optical receiver according to another exemplaryembodiment of the present invention.

[0043]FIG. 19 is a logic flow diagram illustrating an exemplarysubprocess for increasing speed to receive upstream optical datasignals.

[0044]FIG. 20 is a logic flow diagram illustrating an exemplarysubprocess for increasing speed to adjust gain between data signals.

[0045]FIG. 21 is a logic flow diagram illustrating a subprocess forincreasing speed to convert optical data signals to electrical datasignals.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0046] An optical transmitter of a subscriber optical interface and anoptical receiver of a laser transceiver node can have time constantsadjusted to a frequency of data that is formatted according to apredetermined network protocol, that is encoded with a predeterminedcoding scheme, and that is transmitted according to a predetermined datatransmit timing scheme. A network protocol according to the presentinvention can comprise a network protocol that breaks up data intopackets

[0047] The high frequency circuits present in the optical transmitterand optical receiver of the present invention can be adjusted formaximum efficiency when supporting data formatted according to apredetermined network protocol comprising Gigabit Ethernet, with apredetermined encoding scheme of 8B/10B encoding, and data that istransmitted according to a predetermined data timing scheme comprisingTDMA. Specifically, the time constants of two driver circuits ofrespective optical transmitters can be adjusted to increase the speed toconvert turn the transmitter on and off.

[0048] Referring now to the drawings, in which like numerals representlike elements throughout the several Figures, aspects of the presentinvention and the illustrative operating environment will be described.

Illustrative Operating Environment

[0049]FIG. 1 is a functional block diagram illustrating an exemplaryoptical network architecture 100 according to the present invention. Theexemplary optical network architecture 100 comprises a data service hub110 that is connected to one or more outdoor laser transceiver nodes120. The laser transceiver nodes 120, in turn, are connected to opticaltaps 130. The optical taps 130 can be connected to a plurality ofsubscriber optical interfaces 140.

[0050] Between respective components of the exemplary optical networkarchitecture 100 are optical waveguides such as optical waveguides 150,160, 170 and 180. The optical waveguides 150-180 are illustrated byarrows with the arrowheads of the lines illustrating exemplarydirections of the data flow between respective components of theillustrative and exemplary optical network 100.

[0051] While only an individual laser transceiver node 120, anindividual optical tap 130, and an individual subscriber opticalinterface 140 are illustrated in FIG. 1, as will become apparent fromFIG. 2, in its corresponding description, a plurality of lasertransceiver nodes 120, optical taps 130, and subscriber opticalinterfaces 140 can be employed without departing from the scope andspirit of the present invention. Typically, in many of the exemplaryembodiments of the present invention, multiple subscriber opticalinterfaces 140 are connected to one or more optical taps 130.

[0052] The outdoor laser transceiver node 120 can allocate additional orreduced bandwidth based upon the demand of one or more subscribers thatuse the subscriber optical interfaces 140. The outdoor laser transceivernode 120 can be designed to withstand outdoor environmental conditionsand can be designed to hang on a strand or fit in a pedestal or “handhole.” The outdoor laser transceiver node can operate in a temperaturerange between minus 40 degrees Celsius to plus 60 degrees Celsius. Thelaser transceiver node 120 can operate in this temperature range byusing passive cooling devices that do not consume power.

[0053] In one exemplary embodiment of the present invention, three trunkoptical waveguides 160, 170, and 180 (that can comprise optical fibers)can conduct optical signals from the data service hub 110 to the outdoorlaser transceiver node 120. It is noted that the term “opticalwaveguide” used in the present application can apply to optical fibers,planar light guide circuits, and fiber optic pigtails and other likeoptical waveguides.

[0054] A first optical waveguide 160 can carry broadcast video and othersignals. The signals can be carried in a traditional cable televisionformat wherein the broadcast signals are modulated onto carriers, whichin turn, modulate an optical transmitter (not shown) in the data servicehub 110. A second optical waveguide 170 can carry downstream targetedservices such as data and telephone services to be delivered to one ormore subscriber optical interfaces 140. In addition to carryingsubscriber-specific optical signals, the second optical waveguide 170can also propagate internet protocol broadcast packets, as is understoodby those skilled in the art.

[0055] In one exemplary embodiment, a third optical waveguide 180 cantransport data signals upstream from the outdoor laser transceiver node120 to the data service hub 110. The optical signals propagated alongthe third optical waveguide 180 can also comprise data and telephoneservices received from one or more subscribers. Similar to the secondoptical waveguide 170, the third optical waveguide 180 can also carry IPbroadcast packets, as is understood by those skilled in the art.

[0056] The third or upstream optical waveguide 180 is illustrated withdashed lines to indicate that it is merely an option or part of oneexemplary embodiment according to the present invention. In other words,the third optical waveguide 180 can be removed. In another exemplaryembodiment, the second optical waveguide 170 propagates optical signalsin both the upstream and downstream directions as is illustrated by thedouble arrows depicting the second optical waveguide 170.

[0057] In such an exemplary embodiment where the second opticalwaveguide 170 propagates bidirectional optical signals, only two opticalwaveguides 160, 170 would be needed to support the optical signalspropagating between the data server's hub 110 in the outdoor lasertransceiver node 120. In another exemplary embodiment (not shown), asingle optical waveguide can be the only link between the data servicehub 110 and the laser transceiver node 120. In such a single opticalwaveguide embodiment, three different wavelengths can be used for theupstream and downstream signals. Alternatively, bi-directional datacould be modulated on one wavelength.

[0058] In one exemplary embodiment, the optical tap 130 can comprise an8-way optical splitter. This means that the optical tap 130 comprisingan 8-way optical splitter can divide downstream optical signals eightways to serve eight different subscriber optical interfaces 140. In theupstream direction, the optical tap 130 can combine the optical signalsreceived from the eight subscriber optical interfaces 140.

[0059] In another exemplary embodiment, the optical tap 130 can comprisea 4way splitter to service four subscriber optical interfaces 140. Yetin another exemplary embodiment, the optical tap 130 can furthercomprise a 4-way splitter that is also a pass-through tap meaning that aportion of the optical signal received at the optical tap 130 can beextracted to serve the 4-way splitter contained therein while theremaining optical energy is propagated further downstream to anotheroptical tap or another subscriber optical interface 140. The presentinvention is not limited to 4-way and 8-way optical splitters. Otheroptical taps having fewer or more than 4-way or 8-way splits are notbeyond the scope of the present invention.

[0060] Referring now to FIG. 2, this figure is a functional blockdiagram illustrating an exemplary optical network architecture 100.

[0061] Each optical tap 130 can comprise an optical splitter. Theoptical tap 130 allows multiple subscriber optical interfaces 140 (suchas single subscriber optical interfaces 140B or multiple ormulti-subscriber optical interfaces 140A) to be coupled to a singleoptical waveguide 150 that is connected to the outdoor laser transceivernodes 120. In one exemplary embodiment, six optical fibers 150 aredesigned to be connected to the outdoor laser transceiver nodes 120. Forthe use of optical taps 130, sixteen subscribers can be assigned to eachof the six optical waveguides 150 that are connected to the outdoorlaser transceiver nodes 120.

[0062] In another exemplary embodiment, twelve optical fibers 150 can beconnected to a respective outdoor laser transceiver node 120 while eightsubscriber optical interfaces 140 are assigned to each of the twelveoptical waveguides 150. Those skilled in the art will appreciate thenumber of subscriber optical interfaces 140 assigned to a particularwaveguide 150 that is connected between the outdoor laser transceivernodes 120 and a subscriber optical interface 140 (by way of the opticaltap 130) can be varied or changed without departing from the scope andspirit of the present invention. Further, those skilled in the artrecognize that the actual number of subscriber optical interfaces 140assigned to a particular optical waveguide is dependent upon the amountof power available on a particular optical waveguide 150.

[0063] As depicted in FIG. 2, many configurations for supplyingcommunication services to subscribers are possible. The combinations ofoptical taps 130 with other optical taps 130 are limitless. With theoptical taps 130, concentrations of distribution optical waveguide 150at the laser transceiver nodes 120 can be reduced. Additionally, thetotal amount of fiber needed to service the subscriber grouping attachedto a subscriber optical interface 140 can also be reduced.

[0064] With the active laser transceiver node 120 of the presentinvention, the distance between the laser transceiver node 120 and thedata service hub 110 can comprise a range between 0 and 80 kilometers.However, the present invention is not limited to this range. Thoseskilled in the art will appreciate that this range can be expanded byselecting various off-the-shelf components that make up several of thedevices of the present system.

[0065] Those skilled in the art will appreciate that otherconfigurations of the optical waveguides disposed between the dataservice hub 110 and outdoor laser transceiver node 120 are not beyondthe scope of the present invention. Because of the bi-directionalcapability of optical waveguides, variations in the number anddirectional flow of the optical waveguides disposed between the dataservice hub 110 and the outdoor laser transceiver node 120 can be madewithout departing from the scope and spirit of the present invention.

[0066] Referring now to FIG. 3, this functional block diagramillustrates an exemplary data service hub 110 of the present invention.The exemplary data service hub 110 illustrated in FIG. 3 is designed fora two trunk optical waveguide system. That is, this data service hub 110of FIG. 3 is designed to send and receive optical signals to and fromthe outdoor laser transceiver node 120 along the first optical waveguide160 and the second optical waveguide 170. With this exemplaryembodiment, the second optical waveguide 170 supports bi-directionaldata flow. In this way, the third optical waveguide 180 discussed aboveis not needed.

[0067] The data service hub 110 can comprise one or more modulators 310,315 that are designed to support television broadcast services. The oneor more modulators 310, 315 can be analog or digital type modulators. Inone exemplary embodiment, there can be at least 78 modulators present inthe data service hub 110. Those skilled in the art will appreciate thatthe number of modulators 310, 315 can be varied without departing fromthe scope and spirit of the present invention.

[0068] The signals from the modulators 310, 315 are combined in acombiner 320 where they are supplied to an optical transmitter 325 wherethe radio frequency signals generated by the modulators 310, 315 areconverted into optical form.

[0069] The optical transmitter 325 can comprise one of Fabry-Perot (F-P)Laser Transmitters, distributed feedback lasers (DFBs), or VerticalCavity Surface Emitting Lasers (VCSELs). However, other types of opticaltransmitters are possible and are not beyond the scope of the presentinvention. With the aforementioned optical transmitters 325, the dataservice hub 110 lends itself to efficient upgrading by usingoff-the-shelf hardware to generate optical signals.

[0070] The optical signals generated by the optical transmitter (oftenreferred to as the unidirectional optical signals) are propagated toamplifier 330 such as an Erbium Doped Fiber Amplifier (EDFA) where theunidirectional optical signals are amplified. The amplifiedunidirectional optical signals are then propagated out of the dataservice hub 110 via a unidirectional signal output port 335 which isconnected to one or more first optical waveguides 160.

[0071] The unidirectional signal output port 335 is connected to one ormore first optical waveguides 160 that support unidirectional opticalsignals originating from the data service hub 110 to a respective lasertransceiver node 120. The data service hub 110 illustrated in FIG. 3 canfurther comprise an Internet router 340. The data service hub 110 canfurther comprise a telephone switch 345 that supports telephony serviceto the subscribers of the optical network system 100. However, othertelephony service such as Internet Protocol telephony can be supportedby the data service hub 110.

[0072] If only Internet Protocol telephony is supported by the dataservice hub 110, then it is apparent to those skilled in the art thatthe telephone switch 345 could be eliminated in favor of lower costVoice over Internet Protocol (VoIP) equipment. For example, in anotherexemplary embodiment (not shown), the telephone switch 345 could besubstituted with other telephone interface devices such as a soft switchand gateway. But if the telephone switch 345 is needed, it may belocated remotely from the data service hub 110 and can be connectedthrough any of several conventional means of interconnection.

[0073] The data service hub 110 can further comprise a logic interface350 that is connected to a laser transceiver node routing device 355.The logic interface 350 can comprise a Voice over Internet Protocol(VoIP) gateway when required to support such a service. The lasertransceiver node routing device 355 can comprise a conventional routerthat supports an interface protocol for communicating with one or morelaser transceiver nodes 120. This interface protocol can comprise onehalf gigabit or faster Ethernet. However, the present invention is notlimited to this protocol. Other network protocols can be used withoutdeparting from the scope and spirit of the present invention. Forexample, other network protocols can include, but are not limited to,Fiber Distributed Data Interface (FDDI) and Digital VideoBroadcasting-Asynchronous Serial Interface (DVB-ASI).

[0074] The logic interface 350 and laser transceiver node routing device355 can read packet headers originating from the laser transceiver nodes120 and the internet router 340. The logic interface 350 can alsotranslate interfaces with the telephone switch 345. After reading thepacket headers, the logic interface 350 and laser transceiver noderouting device 355 can determine where to send the packets ofinformation.

[0075] The laser transceiver node routing device 355 can supplydownstream data signals to respective optical transmitters 325. The datasignals converted by the optical transmitters 325 can then be propagatedto a bi-directional splitter 360. The optical signals sent from theoptical transmitter 325 into the bi-directional splitter 360 can then bepropagated towards a bi-directional data input/output port 365 that isconnected to a second optical waveguide 170 that supports bi-directionaloptical data signals between the data service hub 110 and a respectivelaser transceiver node 120. Upstream optical signals received from arespective laser transceiver node 120 can be fed into the bi-directionaldata input/output port 365 where the optical signals are then forwardedto the bi-directional splitter 360.

[0076] From the bi-directional splitter 360, respective opticalreceivers 370 can convert the upstream optical signals into theelectrical domain. The upstream electrical signals generated byrespective optical receivers 370 are then fed into the laser transceivernode routing device 355. Each optical receiver 370 can comprise one ormore photoreceptors or photodiodes that convert optical signals intoelectrical signals.

[0077] When distances between the data service hub 110 and respectivelaser transceiver nodes 120 are modest, the optical transmitters 325 canpropagate optical signals at 1310 nm. But where distances between thedata service hub 110 and the laser transceiver node are more extreme,the optical transmitters 325 can propagate the optical signals atwavelengths of 1550 nm with or without appropriate amplificationdevices.

[0078] Those skilled in the art will appreciate that the selection ofoptical transmitters 325 for each circuit may be optimized for theoptical path lengths needed between the data service hub 110 and theoutdoor laser transceiver node 120. Further, those skilled in the artwill appreciate that the wavelengths discussed are practical but areonly illustrative in nature. In some scenarios, it may be possible touse communication windows at 1310 and 1550 nm in different ways withoutdeparting from the scope and spirit of the present invention. Further,the present invention is not limited to a 1310 and 1550 nm wavelengthregions. Those skilled in the art will appreciate that smaller or largerwavelengths for the optical signals are not beyond the scope and spiritof the present invention.

[0079] Referring now to FIG. 4, this Figure illustrates a functionalblock diagram of an exemplary outdoor laser transceiver node 120 of thepresent invention. In this exemplary embodiment, the laser transceivernode 120 can comprise a optical signal input port 405 that can receiveoptical signals propagated from the data service hub 110 that arepropagated along a first optical waveguide 160. The optical signalsreceived at the optical signal input port 405 can comprise broadcastvideo data. The optical signals received at the input port 405 arepropagated to an amplifier 410 such as an Erbium Doped Fiber Amplifier(EDFA) in which the optical signals are amplified. The amplified opticalsignals are then propagated to a splitter 415 that divides the broadcastvideo optical signals among diplexers 420 that are designed to forwardoptical signals to predetermined groups of subscribers.

[0080] The laser transceiver node 120 can further comprise abi-directional optical signal input/output port 425 that connects thelaser transceiver node 120 to a second optical waveguide 170 thatsupports bi-directional data flow between the data service hub 110 andlaser transceiver node 120. Downstream optical signals flow through thebi-directional optical signal input/output port 425 to an opticalwaveguide transceiver 430 that converts downstream optical signals intothe electrical domain. The optical waveguide transceiver furtherconverts upstream electrical signals into the optical domain. Theoptical waveguide transceiver 430 can comprise an optical/electricalconverter and an electrical/optical converter.

[0081] Downstream and upstream electrical signals are communicatedbetween the optical waveguide transceiver 430 and an optical tap routingdevice 435. The optical tap routing device 435 can manage the interfacewith the data service hub optical signals and can route or divide orapportion the data service hub signals according to individual tapmultiplexers 440 that communicate optical signals with one or moreoptical taps 130 and ultimately one or more subscriber opticalinterfaces 140. It is noted that tap multiplexers 440 operate in theelectrical domain to modulate laser transmitters in order to generateoptical signals that are assigned to groups of subscribers coupled toone or more optical taps.

[0082] Optical tap routing device 435 is notified of available upstreamdata packets as they arrive, by each tap multiplexer 440. The opticaltap routing device is connected to each tap multiplexer 440 to receivethese upstream data packets. The optical tap routing device 435 relaysthe packets to the data service hub 110 via the optical waveguidetransceiver 430. The optical tap routing device 435 can build a lookuptable from these upstream data packets coming to it from all tapmultiplexers 440 (or ports), by reading the source IP address of eachpacket, and associating it with the tap multiplexer 440 through which itcame. This lookup table can then be used to route packets in thedownstream path. As each packet comes in from the optical waveguidetransceiver 430, the optical tap routing device looks at the destinationIP address (which is the same as the source IP address for the upstreampackets). From the lookup table the optical tap routing device candetermine which port is connected to that IP address, so it sends thepacket to that port. This can be described as a normal layer 3 routerfunction as is understood by those skilled in the art.

[0083] The optical tap routing device 435 can assign multiplesubscribers to a signal port. More specifically, the optical tap routingdevice 435 can service groups of subscribers with correspondingrespective signal ports. The optical taps 130 logically coupled torespective tap multiplexers 440 can supply downstream optical signals topre-assigned groups of subscribers who receive the downstream opticalsignals with the subscriber optical interfaces 140.

[0084] In other words, the optical tap routing device 435 can determinewhich tap multiplexer 440 is to receive a downstream electrical signal,or identify which of a plurality of optical taps 130 propagated anupstream optical signal (that is converted to an electrical signal). Theoptical tap routing device 435 can format data and implement theexemplary protocol required to send and receive data from eachindividual subscriber connected to a respective optical tap 130. Theexemplary protocol can comprise Gigabit Ethernet having a predeterminedcoding scheme of 8B/10B encoding and a downstream timing scheme of timedivision multiplexing and an upstream timing scheme of time divisionmultiple access (TDMA). The optical tap routing device 435 can comprisea computer or a hardwired apparatus that executes a program defining aprotocol and the predetermined timing scheme for communications withgroups of subscribers assigned to individual ports.

[0085] Exemplary embodiments of programs defining the protocol andpredetermined timing scheme are discussed in the following copending andcommonly assigned non-provisional patent applications, the entirecontents of which are hereby incorporated by reference: “Method andSystem for Processing Downstream Packets of an Optical Network,” filedon Oct. 26, 2001 in the name of Stephen A. Thomas et al. and assignedU.S. Ser. No. 10/045,652; and “Method and System for Processing UpstreamPackets of an Optical Network,” filed on Oct. 26, 2001 in the name ofStephen A. Thomas et al. and assigned U.S. Ser. No. 10/045,584.

[0086] The signal ports of the optical tap routing device are connectedto respective tap multiplexers 440. With the optical tap routing device435, the laser transceiver node 120 can adjust a subscriber's bandwidthon a subscription basis or on an as-needed or demand basis. The lasertransceiver node 120 via the optical tap routing device 435 can offerdata bandwidth to subscribers in preassigned increments. For example,the laser transceiver node 120 via the optical tap routing device 435can offer a particular subscriber or groups of subscribers bandwidth inunits of 1, 2, 5, 10, 20, 50, 100, 200, and 450 Megabits per second(Mb/s). Those skilled in the art will appreciate that other subscriberbandwidth units are not beyond the scope of the present invention.

[0087] Electrical signals are communicated between the optical taprouting device 435 and respective tap multiplexers 440. The tapmultiplexers 440 propagate optical signals to and from various groupingsof subscribers. Each tap multiplexer 440 is connected to a respectiveoptical transmitter 325. As noted above, each optical transmitter 325can comprise one of a Fabry-Perot (F-P) laser, a distributed feedbacklaser (DFB), or a Vertical Cavity Surface Emitting Laser (VCSEL). Otherlaser technologies may be used within the scope of the invention. Theoptical transmitters produce the downstream optical signals that arepropagated towards the subscriber optical interfaces 140. Each tapmultiplexer 440 is also coupled to an optical receiver 370. Each opticalreceiver 370, as noted above, can comprise photoreceptors orphotodiodes. Since the optical transmitters 325 and optical receivers370 can comprise off-the-shelf hardware to generate and receiverespective optical signals, the laser transceiver node 120 lends itselfto efficient upgrading and maintenance to provide significantlyincreased data rates.

[0088] Each optical transmitter 325 and each optical receiver 370 areconnected to a respective bi-directional splitter 360. Eachbi-directional splitter 360 in turn is connected to a diplexer 420 whichcombines the unidirectional optical signals received from the splitter415 with the downstream optical signals received from respective opticaltransmitter 325. In this way, broadcast video services as well as dataservices can be supplied with a single optical waveguide such as adistribution optical waveguide 150 as illustrated in FIG. 2. In otherwords, optical signals can be coupled from each respective diplexer 420to a combined signal input/output port 445 that is connected to arespective distribution optical waveguide 150.

[0089] Unlike the conventional art, the laser transceiver node 120 doesnot employ a conventional router. The components of the lasertransceiver node 120 can be disposed within a compact electronicpackaging volume. For example, the laser transceiver node 120 can bedesigned to hang on a strand or fit in a pedestal similar toconventional cable TV equipment that is placed within the “last,” mileor subscriber proximate portions of a network. It is noted that theterm, “last mile,” is a generic term often used to describe the lastportion of an optical network that connects to subscribers.

[0090] Also because the optical tap routing device 435 is not aconventional router, it does not require active temperature controllingdevices to maintain the operating environment at a specific temperature.In other words, the laser transceiver node 120 can operate in atemperature range between minus 40 degrees Celsius to 60 degrees Celsiusin one exemplary embodiment.

[0091] While the laser transceiver node 120 does not comprise activetemperature controlling devices that consume power to maintaintemperature of the laser transceiver node 120 at a single temperature,the laser transceiver node 120 can comprise one or more passivetemperature controlling devices 450 that do not consume power. Thepassive temperature controlling devices 450 can comprise one or moreheat sinks or heat pipes that remove heat from the laser transceivernode 120.

[0092] Those skilled in the art will appreciate that the presentinvention is not limited to these exemplary passive temperaturecontrolling devices. Further, those skilled in the art will alsoappreciate the present invention is not limited to the exemplaryoperating temperature range disclosed. With appropriate passivetemperature controlling devices 450, the operating temperature range ofthe laser transceiver node 120 can be reduced or expanded.

[0093] In addition to the laser transceiver node's 120 ability towithstand harsh outdoor environmental conditions, the laser transceivernode 120 can also provide high speed symmetrical data transmissions. Inother words, the laser transceiver node 120 can propagate the same bitrates downstream and upstream to and from a network subscriber. This isyet another advantage over conventional networks, which typically cannotsupport symmetrical data transmissions as discussed in the backgroundsection above. Further, the laser transceiver node 120 can also serve alarge number of subscribers while reducing the number of connections atboth the data service hub 110 and the laser transceiver node 120 itself.

[0094] The laser transceiver node 120 also lends itself to efficientupgrading that can be performed entirely on the network side or dataservice hub 110 side. That is, upgrades to the hardware forming thelaser transceiver node 120 can take place in locations between andwithin the data service hub 110 and the laser transceiver node 120. Thismeans that the subscriber side of the network (from distribution opticalwaveguides 150 to the subscriber optical interfaces 140) can be leftentirely in-tact during an upgrade to the laser transceiver node 120 ordata service hub 110 or both. The following is provided as an example ofan upgrade that can be employed utilizing the principles of the presentinvention. In one exemplary embodiment of the invention, the subscriberside of the laser transceiver node 120 can service six groups of 16subscribers each for a total of up to 96 subscribers. Each group of 16subscribers can share a data path of about 450 Mb/s speed. Six of thesepaths represents a total speed of 6×450=2.7 Gb/s. In the most basicform, the data communications path between the laser transceiver node120 and the data service hub 110 can operate at 1 Gb/s. Thus, while thedata path to subscribers can support up to 2.7 Gb/s, the data path tothe network can only support 1 Gb/s. This means that not all of thesubscriber bandwidth is useable. This is not normally a problem due tothe statistical nature of bandwidth usage.

[0095] An upgrade could be to increase the 1 Gb/s data path speedbetween the laser transceiver node 120 and the data service hub 110.This may be done by adding more 1 Gb/s data paths. Adding one more pathwould increase the data rate to 2 Gb/s, approaching the totalsubscriber-side data rate. A third data path would allow thenetwork-side data rate to exceed the subscriber-side data rate. In otherexemplary embodiments, the data rate on one link could rise from 1 Gb/sto 2 Gb/s then to 10 Gb/s, so when this happens, a link can be upgradedwithout adding more optical links.

[0096] The additional data paths (bandwidth) may be achieved by any ofthe methods known to those skilled in the art. It may be accomplished byusing a plurality of optical waveguide transceivers 430 operating over aplurality of optical waveguides, or they can operate over one opticalwaveguide at a plurality of wavelengths, or it may be that higher speedoptical waveguide transceivers 430 could be used as shown above. Thus,by upgrading the laser transceiver node 120 and the data service hub 110to operate with more than a single 1 Gb/s link, a system upgrade iseffected without having to make changes at the subscribers' premises.

[0097] Referring now to FIG. 5, this Figure is a functional blockdiagram illustrating an optical tap 130 connected to a subscriberoptical interface 140 by a single optical waveguide 150 according to oneexemplary embodiment of the present invention. The optical tap 130 cancomprise a combined signal input/output port 505 that is connected toanother distribution optical waveguide that is connected to a lasertransceiver node 120. As noted above, the optical tap 130 can comprisean optical splitter 510 that can be a 4-way or 8-way optical splitter.Other optical taps having fewer or more than 4-way or 8-way splits arenot beyond the scope of the present invention. The optical tap candivide downstream optical signals to serve respective subscriber opticalinterfaces 140. In the exemplary embodiment in which the optical tap 130comprises a 4-way optical tap, such an optical tap can be of thepass-through type, meaning that a portion of the downstream opticalsignals is extracted or divided to serve a 4-way splitter containedtherein, while the rest of the optical energy is passed furtherdownstream to other distribution optical waveguides 150.

[0098] The optical tap 130 is an efficient coupler that can communicateoptical signals between the laser transceiver node 120 and a respectivesubscriber optical interface 140. Optical taps 130 can be cascaded, orthey can be connected in a star architecture from the laser transceivernode 120. As discussed above, the optical tap 130 can also route signalsto other optical taps that are downstream relative to a respectiveoptical tap 130.

[0099] The optical tap 130 can also connect to a limited or small numberof optical waveguides so that high concentrations of optical waveguidesare not present at any particular laser transceiver node 120. In otherwords, in one exemplary embodiment, the optical tap can connect to alimited number of optical waveguides 150 at a point remote from thelaser transceiver node 120 so that high concentrations of opticalwaveguides 150 at a laser transceiver node can be avoided. However,those skilled in the art will appreciate that the optical tap 130 can beincorporated within the laser transceiver node 120.

[0100] The subscriber optical interface 140 functions to convertdownstream optical signals received from the optical tap 130 into theelectrical domain that can be processed with appropriate communicationdevices. The subscriber optical interface 140 further functions toconvert upstream electrical signals into upstream optical signals thatcan be propagated along a distribution optical waveguide 150 to theoptical tap 130. The subscriber optical interface 140 can comprise anoptical diplexer 515 that divides the downstream optical signalsreceived from the distribution optical waveguide 150 between abi-directional optical signal splitter 520 and an analog opticalreceiver 525. A service disconnect switch 527 can be positioned betweenthe analog optical receiver 525 and modulated RF unidirectional signaloutput 535.

[0101] The optical diplexer 515 can receive upstream optical signalsgenerated by a digital optical transmitter 530. The digital opticaltransmitter 530 converts electrical binary/digital signals to opticalform so that the optical signals can be transmitted back to the dataservice hub 110. Conversely, the digital optical receiver 540 convertsoptical signals into electrical binary/digital signals so that theelectrical signals can be handled by processor 550.

[0102] The analog optical receiver 525 can convert the downstreambroadcast optical video signals into modulated RF television signalsthat are propagated out of the modulated RF unidirectional signal output535. The modulated RF unidirectional signal output 535 can feed to RFreceivers such as television sets (not shown) or radios (not shown). Theanalog optical receiver 525 can process analog modulated RF transmissionas well as digitally modulated RF transmissions for digital TVapplications.

[0103] The bi-directional optical signal splitter 520 can propagatecombined optical signals in their respective directions. That is,downstream optical signals entering the bi-directional optical splitter520 from the optical diplexer 515, are propagated to the digital opticalreceiver 540. Upstream optical signals entering it from the digitaloptical transmitter 530 are sent to optical diplexer 515 and then tooptical tap 130. The bi-directional optical signal splitter 520 isconnected to a digital optical receiver 540 that converts downstreamdata optical signals into the electrical domain. Meanwhile thebi-directional optical signal splitter 520 is also connected to adigital optical transmitter 530 that converts upstream electricalsignals into the optical domain.

[0104] The digital optical receiver 540 can comprise one or morephotoreceptors or photodiodes that convert optical signals into theelectrical domain. The digital optical transmitter can comprise one ormore lasers such as the Fabry-Perot (F-P) Lasers, distributed feedbacklasers, and Vertical Cavity Surface Emitting Lasers (VCSELs).

[0105] The digital optical receiver 540 and digital optical transmitter530 are connected to a processor 550 that selects data intended for theinstant subscriber optical interface 140 based upon an embedded address.The data handled by the processor 550 can comprise one or more oftelephony and data services such as an Internet service. The processor550 is connected to a telephone input/output 555 that can comprise ananalog interface.

[0106] The processor 550 is also connected to a data interface 560 thatcan provide a link to computer devices, set top boxes, ISDN phones, andother like devices. Alternatively, the data interface 560 can comprisean interface to a Voice over Internet Protocol (VoIP) telephone orEthernet telephone. The data interface 560 can comprise one ofEthernet's (10BaseT, 100BaseT, Gigabit) interface, HPNA interface, auniversal serial bus (USB) an IEEE1394 interface, an ADSL interface, andother like interfaces.

Upstream and Downstream Optical Communications with Predetermined TimingSchemes

[0107] Referring now to FIG. 6, this figure illustrates exemplary timingschemes for downstream and upstream optical communications between thelaser transceiver node 120 and the subscriber optical interface 140according to one exemplary embodiment of the present invention. Fordownstream communications, the outdoor laser transceiver node 120 cantransmit data according to a time division multiplexing (TDM) scheme fordata segments A, B, C, and D that are sent serially one after another.Opposite to the downstream optical communication 600, the subscriberoptical interface 140 generates upstream optical communications 605 thatcan comprise data segments E, F, G, and H that are not transmittedimmediately one after another because of transition time intervals 610that are interposed between each of the data segments E, F, G, and H.

[0108] Without the present invention, conventional hardware and softwarethat produce an upstream optical signal utilizing a predetermined timingscheme such as TDMA has transition time intervals 610 that are fairlylarge and detract from the efficiency at which data is communicated fromsubscriber optical interfaces to a data service hub. However, with thepresent invention, the transition time intervals 610 can besubstantially reduced such that upstream optical communications fromsubscriber optical interfaces 140 to data service hubs 110 areoptimized.

[0109] Referring now to FIG. 7, this figure is a functional blockdiagram that describes how the transition time intervals 610 arecreated. The transition time intervals 610 are produced when a firstdigital optical transmitter 530, powers down after sending its data Eand when a second digital optical transmitter 5302 starts to power upits optical transmitter for transmitting its data F. In the timingscheme diagram of FIG. 7, time 700 is advancing to the right. For thepurposes of illustration, only three digital optical transmitters 530 ofthree subscriber optical interfaces 140 are illustrated, although thoseskilled in the art recognize that additional subscriber opticalinterfaces 140 with respective digital optical transmitters 530 can beemployed without departing from the scope and spirit of the presentinvention.

[0110] The top region 705 of the diagram illustrates exemplary TDMA timeslots in which one subscriber optical interface 140 after another isauthorized to transmit data in an upstream direction. Digital opticaltransmitters 530 ₁, 530 ₂, and 530 ₃ are located in respectivesubscriber optical interfaces 140 ₁, 140 ₂, and 140 ₃. At the beginningof the transmit time for each subscriber optical interface 140, a run-insequence 710 is transmitted. This sequence 710 is a known data patternusually transmitted to allow the circuits described below to settle tothe correct operating point, and which will allow a clock and opticalreceiver 370 to lock on to incoming data. In other words, the transitiontime interval 610 can comprise this run-in sequence 710 where noreadable data is transmitted until the conclusion of the run-in sequence710. In addition to the run-in sequence 710, the transition timeinterval 610 can further comprise dead time between each respective datasegment E, F, G. The dead time 715 is necessary in some instances tocompensate for clock inaccuracies and time ambiguities in the turn-onand turn-off of each digital optical transmitter 530.

[0111] The second row 720 of FIG. 7 illustrates the state of eachdigital optical transmitter during a time its respective subscriberoptical interface 140 is authorized to send data during thepredetermined timing scheme of TDMA. The second row 720 of FIG. 7 canideally comprise two states: up, meaning the transmitter 530 istransmitting at normal power, and down, meaning the digital opticaltransmitter 530 is not transmitting. However, in reality, each digitaloptical transmitter 530 requires to time to power up to the maximumamount of power when it is turned on. And similarly, each digitaloptical transmitter 530 requires some time to reduce its power to zerowhen it is turned off.

[0112] The power ramp down period 725 of the first digital opticaltransmitter 530 ₁ can overlap the power ramp-up period 730 for thesecond digital optical transmitter 530 ₂. In other words, while firsttransmitter 530 ₁ is reducing its power, the second optical transmitter530 ₂ is turning on and increasing its power level as indicated in thepower ramp-up period 730. When the power for a respective digitaloptical transmitter 530 reaches its maximum, the circuits responsiblefor generating this power will settle to their respective quiescentstates 735 illustrated with a flat, nonsloping line segment.

[0113] The third row 740 of FIG. 7 illustrates the upstream opticalsignal 605 from the vantage point of a single optical receiver 370 of alaser transceiver node 120. The transition time interval 610 for theoptical receiver 370 can comprise two components. A first component ofthe transition time interval 610 can comprise an adjustment of anautomatic gain control (AGC) operating point. Signals from each digitaloptical transmitter 530 can arrive at the optical receiver 370 atslightly different power levels. This variation in power levels can beattributed to normal production variations of the components producingthe upstream optical energy and the output power of the transmitters 530as well as varying losses between each transmitter 530 and the opticalreceiver 370.

[0114] Because of different power levels, many optical receivers 370employ AGC circuits similar in concept to those found in RF radioreceivers. AGC circuits can adjust the gain of an amplifier such thatthe output signal level is suitable for application for a next stage ofprocessing regardless of the varying level of input optical power.

[0115] When switching the receiving of data from one transmitter 530 toanother, an AGC circuit usually needs some time to readjust itsoperating level. This readjustment time forms part of the transitiontime interval 610 for the optical receiver 370 and can occur duringrun-in time 710. Further, an AC coupling stage can occur in each opticalreceiver 370. This AC coupling stage can shift the incoming operatingpower point from one optical transmitter 530 to another. This ACcoupling stage also forms a portion of the transition time interval 610as perceived by the optical receiver 370.

[0116] Graph 740 of FIG. 7 illustrates uploading power points of asingle optical receiver 370 that receives signals from various digitaloptical transmitters 530. Graph 740 is intended to illustrate acomposite picture of the automatic gain control adjustment and ACcoupling that occurs during the transition time interval 610 when thereis a switch between data generated by one optical transmitter 530 toanother. The transmission time interval 610 for graph 740 furthercomprises an indecision time 750 that can occur when the received powerfrom a first transmitter 530 ₁ is turning off while the power fromanother second transmitter 530 ₂ is turning on. The operating pointduring indecision time 750 can fluctuate or is inconsistent since thetypically both transmitters 530 ₁, 530 ₂ are in a state of transition.

[0117] After the first transmitter 530 ₁ has turned off and the secondoptical transmitter 530 ₂ has stabilized its output, then the opticalreceiver 370 can still require some time 755 to settle the AC couplingand the automatic gain control. Further, it is noted that the flat orquiescent portions 760 of the graph 740 do not comprise the sameamplitude of power level for each of the subscriber optical interfaces140. This difference in power level between respective subscriberoptical interfaces 140 is a result of the difference in the receivedpower level from each of the three optical transmitters 530.

[0118] The adjustment period 755 can occur during the same time that therun-in signals 710 are being transmitted to the optical receiver 370.The run-in signals 710 can be very important to allow an opticalreceiver 370 to arrive at its correct quiescent state. Each run-insignal 710 is also necessary to allow a respective transmitter 530 toreset itself to a correct operating level.

[0119] While all the various setting issues identified above aredescribed somewhat serially in FIG. 7, in practice all of the settlingevents at the optical transmitter 530 and at the optical receiver 370usually occur simultaneously. One exemplary aspect of the presentinvention is to force or drive all of the settling events illustrated inFIG. 7 to happen faster such that the transition time interval 610 issubstantially reduced or eliminated. It is noted that during eachtransition time interval 610, no data can be transmitted between arespective subscriber optical interface 140 and the laser transceivernode 120. In the conventional art, when transition time intervals in apredetermined timing scheme such as TDMA become large, then thetransition time interval 610 can seriously limit the ability andefficiency of the optical communication system to transfer data betweenthe subscriber optical interface and the data service hub 110.

Low Occupied Frequency Data Discovery

[0120] Referring now to FIG. 8, the graph 800 illustrates the occupiedfrequency of data that is formatted according to conventional opticalnetwork protocols such as SONET compared to data that is formatted to anexemplary network protocol encoded with a predetermined coding schemeaccording to the present invention. As noted above this diagramillustrates a frequency spectrum of conventional network protocols, aswell as the exemplary network protocol according to the presentinvention.

[0121] The inventors have discovered that data formatted according to anexemplary network protocol with a predetermined coding scheme accordingto the present invention does not extend to as low as an occupiedfrequency as does the data formatted with the conventional opticalnetwork protocol such as SONET. Specifically, the first solid slantedline 805 represents data that is formatted according to conventionaloptical network protocols such as SONET.

[0122] At the exemplary speed of half gigabit per second data rate, theminimum frequency of a SONET signal is approximately lower than 4.3 MHz,and for Ethernet with 8B/10B encoding, is approximately 52 MHz. Suitabletime constants for SONET signals at this data rate are approximately aminimum of 184 nanoseconds, and for Gigabit Ethernet are approximately15 nanoseconds. Both are based on a time constant corresponding toapproximately five times the minimum occupied frequency.

[0123] It is noted that in the exemplary system, 8B/10B encodingspecified for Gigabit Ethernet is used, though the actual data rate isone half Gigabit before 8B/10B encoding, or 625 Mb/s after 8B/10Bencoding. This is understood by those skilled in the art. Thus, whenreference is made in this description to Gigabit Ethernet, it isunderstood to those of ordinary skill in the art that the exemplaryembodiment can operate at one half this rate using the same 8B/10Bencoding, though other rates are certainly possible and within the scopeand spirit of the present invention.

[0124] Meanwhile, the dashed slanted line 810 represents the startingand lowest frequency for data formatted according to a network protocolencoded with a predetermined coding scheme. According to one exemplaryaspect of the present invention, the inventors of the presentapplication have discovered that the network protocol comprising GigabitEthernet having a predetermined encoding scheme such as 8B/10B encodingdoes not extend to as low an occupied frequency as that of dataformatted according to conventional optical network protocols such asSONET.

[0125] Since the occupied frequency of the network optical protocol ofthe present invention does not extend to as low a frequency as does theconventional optical network protocol, the present invention can takeadvantage of such a property so that the time constant of high frequencycircuits that handle data according to these formats can be optimizedsuch that an increase in speed at which the high frequency circuits cantransition from one subscriber optical interface to anothersubstantially improves the efficiency and operation of upstream datacommunications with a data service hub 110.

[0126] The inventors have identified a few factors that can account forhow quickly an optical data system can transition from one digitaloptical transmitter 530 to another. These factors can include:

[0127] (1) The speed at which a transmitter 530 completing itstransmission can turn off; (2) the speed at which a transmitter 530 canturn on; and (3) the speed at which a transmitter 530 commencing itstransmission can settle certain internal coupling parameters so that itis transmitting valid and perceptible data via the laser transceivernode 120 to the data service hub 110; and (4) the speed at which theoptical receiver 370 can recover from receiving signals from onetransmitter 530 to the next; setting its base line automatic gaincontrol signal, and the AC coupling to be correct for the commencing orinitiating transmitter 530.

Exemplary Optical Transmitter Adjusted to Data Frequency ofPredetermined Protocol

[0128] Referring now to FIG. 9, this Figure illustrates a functionalblock diagram of the digital optical transmitter 530 positioned withinthe subscriber optical interface 140. The digital optical transmitter530 can comprise a driver circuit 900, a laser transmitter circuit 905,a power level circuit 910, and optional voltage forcing circuit 915. Thedriver circuit 900 can receive serial electrical data 920 from aserial/de-serializer (SERDES) 930. SERDES 930 receives parallel datafrom the processor 550 and converts the data to a serial format. Boththe serial data and parallel data are propagated according to a networkprotocol at one-half a Gigabit per second or faster with a predeterminedencoding scheme. Further details of the driver circuit 900 will bedescribed below with respect to FIG. 10.

[0129] The serial data output from the driver circuit 900 modulates thelaser transmitter 905. The laser transmitter 905 can comprise a laserdiode. However, other types of laser transmitters 905 are not beyond thescope of the present invention. Other types of laser transmitters 905,include, but are not limited to, Fabry-Perot (F-P) Laser Transmitters,distributed feedback lasers (DFBs), or Vertical Cavity Surface EmittingLasers (VCSELs). It is also possible to use emitters that emit signalsover a wider range of wavelengths, such as light emitting diodes.

[0130] The bias or power level circuit 910 produces the electricalcurrent needed to power the laser transmitter 905. Both the power levelcircuit 910 and the driver circuit 900 are controlled by the processor550. The processor 550 activates switches that turn on and off for thedriver circuit 900 and power level circuit 910. The driver circuit 900and power level circuit 910 are usually switched on and off at the sametimes. In other words, the switching positions for each of the switchesassociated with the respective driver circuit 900 and the power levelcircuit 910 are turned on and off at the same time by the processor 550.

[0131] The processor 550 also forwards parallel data to aserial/de-serializer (SERDES) 930. The SERDES 930 converts the paralleldata into serial data which is fed into the driver circuit 900 of thetransmitter 530.

[0132] Once the laser transmitter 905 is modulated by the driver circuit900, upstream optical data propagated according to a predetermined timescheme and a network protocol and encoded with a predetermined codingscheme is produced. It is noted that the processor 550 activates thedriver circuit 900 and bias and power level circuit 910 at predeterminedtimes according to the predetermined timing scheme.

[0133] As noted above, the predetermined timing scheme can comprise timedivision multiple access (TDMA). However, other predetermined timingschemes such as time division multiplexing (TDM) code division multipleaccess (CDMA), and other like timing schemes are not beyond the scopeand spirit of the present invention when such timing schemes involveswitching between a plurality of transmitters 530.

[0134] It is noted that the driver circuit 900, the power level circuit910, and voltage forcing circuit 915 typically comprise ac coupled highfrequency electrical circuits that have a coupling time constant thatcan be adjusted in accordance with the scope and spirit of the presentinvention.

[0135] Referring now back to FIG. 10, this Figure is a functional blockdiagram illustrating some discrete components of an exemplary drivercircuit 900. The exemplary driver circuit 900 can comprise a first highpass filter circuit 1000 having a first time constant. The drivercircuit 900 can further comprise an amplifier 1010 and second high passfilter circuit 1020 having a second time constant. The first high passfilter circuit 1000 can receive the electrical data 920. The electricaldata 920 then flows through the amplifier 1010 and through the secondhigh pass filter circuit 1020. The second high pass filter circuit 1020produces data in accordance with a second time constant.

[0136] The second high pass filter circuit 1020 forwards the filtereddata to the laser transmitter diode 905. Further details of the firsthigh pass filter circuit 1000, amplifier 1010, and second high passfilter circuit 1020 will be discussed below with respect to FIG. 11. Thepresent invention is not limited to the number and types of filters andamplifiers 1010 illustrated. The driver circuit 900 can comprise anynumber of different electrical circuits that are designed to modulatelaser transmitter diodes 905. According to the present invention, thetime constant of the first high pass filter circuit 1000 and the timeconstant of the second high pass filter circuit 1020 can be adjusted.

[0137] Referring now to FIG. 11, this Figure illustrates one exemplaryelectrical circuit for the digital optical transmitter 530. The digitaloptical transmitter 530 can comprise the driver circuit 900, lasertransmitter circuit 905, power level circuit 910, and an optionalvoltage forcing circuit 915. The driver circuit 900 in one exemplaryembodiment comprises a first high pass filter circuit 1000 with a firsttime constant, an amplifier 1010, and a second high pass filter circuit1020 with a second time constant.

[0138] The first high pass filter circuit 1000 can comprise twocapacitors C1, C2 that can couple opposite phases of a balanced signal,as is understood by those skilled in the art. The first high pass filtercircuit 1000 may further comprise a terminating Resistor R₁. Theamplifier 1010 can convert the incoming data from balanced tounbalanced, and set the current to what is needed to effect propermodulating current in an exemplary laser diode 1100. The data amplifier1010 can comprise an operational amplifier 1010 whose output can berouted through switch S1.

[0139] Switch S1 can interrupt data when the digital optical transmitter530 is switched off by the processor 550. From switch S1, data can becapacitively coupled through third capacitor C3 to cathode of theexemplary laser diode 1100. The capacitive coupling of the thirdcapacitor C3 can remove any DC off-set, and also permitting the powerlevel loop 910 to control the average power output of laser diode 1100.The third capacitor C3 forms a portion of the second high pass filtercircuit 1020 having a second time constant.

[0140] The second high pass filter circuit 1020 further comprises afirst inductor L1 and a second switch S2. The second high pass filtercircuit 1020 has a second time constant that is a function of the thirdcapacitor C3, and the first inductor L1. The second time constant canalso be a function of any equivalent resistance that may be generated bythe wires, the resistance of laser diode 1100, and other like componentsthat may produce some form of resistance. Switch S1 and the secondswitch S2 operate in parallel with one another meaning that when thefirst switch S1 is “on,” the second switch S2 is also turned “on.” Thefirst and second switches S1, S2 are controlled by the processor 550.

[0141] The first inductor L1 can isolate the power leveling circuit 910from the data introduced to the laser diode 1100 where the thirdcapacitor C3 feeds the data into the diode 1100. The first inductor L1usually comprises a high impedance at all frequencies at which any datasignal power exists. This can include the lowest frequencies of the datasignal, where the highest inductance is usually demanded of the firstinductor L1. Those skilled in the art will appreciate that the secondhigh pass filter circuit 1020 can comprise different circuit elementsthan those illustrated in FIG. 11, without departing from the scope andspirit of the present invention.

[0142] The optical transmitter 905 can further comprise a monitor diode1105 that receives optical power from the laser diode and can produce acurrent proportional to the light level of the diode 1100. This currentcan be converted to a voltage in a second resistor R₂ of the power levelcircuit 910. The voltage in the second resistor R₂ of the power levelcircuit 910 can be averaged by a fourth capacitor C4.

[0143] The power level circuit 910 further comprises a second amplifier1110 that generates any necessary voltage to correct the current flowingthrough diode 1100 and through the first inductor L1. This currentflowing through the diode 1100 is a result of the voltage produced by asecond amplifier 1110 produces the desired average output light level ofdiode 1100. The power level circuit 910 has a third time constantrelative to the entire optical transmitter that is a function of thefourth capacitor C4 and the second resistor R2. The fourth capacitor C4may be considered as a low pass filter of the power level circuit 910.

[0144] The power leveling circuit 910 forces the averaged value of theoptical power produced by the diode 1100 to be at the desired powerlevel, which desired power representation is supplied to the secondamplifier 1110 first input 1115. This desired voltage is represented bythe notation “V_(REF)” illustrated in FIG. 11. The power level circuit910 is not limited to the circuit elements illustrated in FIG. 11. Othercircuit elements for the power level circuit 910 are not beyond thescope and spirit of the present invention.

[0145] It is noted that additional compensating circuit components canbe employed without departing from the scope and spirit of the presentinvention. FIG. 11 illustrates enough circuit elements to demonstrate atleast one aspect of the present invention. Those skilled in the art willappreciate that additional circuit elements may be required to build afunctional circuit.

[0146] The operation of the driver circuit, the laser transmittercircuit 905, and the power level circuit 910 are described as follows:the first switch S1 is closed in order to start signal current flowingthrough the laser diode 1100, which will start producing some opticalpower. Some lag or delay will exist to start producing this opticalpower as a result of the operation of the second time constant,involving C3.

[0147] The inductance of the first inductor L1 is needed in order toprovide direct current (DC) in the diode 1100. The first inductor L1 canalso prevent any bias signal from being propagated to the secondamplifier 1110. Those skilled in the art recognize that some time isneeded for current to start flowing through the first inductor L1 whenthe diode 1100 is turned on.

[0148] Time is also needed to build up the proper charge on the fourthcapacitor C4 of the power leveling circuit 910. While the time needed bythe above identified circuit elements to achieve their proper operatinglevel may be measured in microseconds, any number of microseconds canhave a substantial impact when transferring data according topredetermined timing schemes such as time division multiple access(TDMA) and at data transfer rates such as one half Gigabit per second.

[0149] When the second switch S2 is closed to activate or connect thepower level circuit 910 to the driver circuit 900 and laser transmittercircuit 905, laser diode 1100 turns on. A direct current (DC) componentis supplied by monitor diode 1105 to charge the fourth capacitor C4. TheDC current flowing across the fourth capacitor C4 of the power levelcircuit 910 may also take some time to charge C4, that can be measuredin microseconds. According to one exemplary aspect of the presentinvention, the time needed to establish charges across capacitors andcurrents through inductors of the aforementioned circuits are minimized.

[0150] The time required to charge each of the capacitors of the variouscircuits of the optical transmitter 530 is dependent on the timeconstants of each of their respective circuits. For example, the timerequired to charge the fourth capacitor C4 to its operating voltage isproportional to the value of the capacitance of the fourth capacitor C4and the value of resistance for the second resistor R2. The time for thethird capacitor C3 of the driver circuit 900 is a function of the thirdcapacitor's C3 capacitance, any equivalent resistance within the linesconnected to the third capacitor C3, and the inductance of the firstinductor L1.

[0151] According to one aspect of the present invention, it has beendetermined that the value of each of the capacitors of each of theindividual circuits discussed above can be adjusted to change the timeconstants of the respective circuits in order to propagate dataformatted according to a predetermined network protocol encoded with thepredetermined coding scheme, and according to a predetermined timingscheme. In other words, according to one exemplary aspect of theinvention, it has been discovered that the time constants of thecircuits discussed above can be customized or adjusted for data that isformatted according to a predetermined network protocol that is encodedwith a predetermined coding scheme.

[0152] Specifically, the predetermined network protocol can comprisehalf Gigabit or faster Ethernet encoded with 8B/10B encoding andtransmitted according to time division multiple access (TDMA). Thoseskilled in the art recognize that a significant portion of opticalequipment on the market as of the filing date of this specification isdesigned to operate with a SONET standard optical network protocol.

[0153] Because this hardware is designed for this specific opticalnetwork protocol, the hardware cannot optimally process data that isformatted with the predetermined network protocol, the predeterminedencoding scheme that is transmitted according to a predetermined timingscheme such as time division multiple access (TDMA) of the presentinvention. Adjusting the time constants of the electrical circuits ofthe present invention is limited to a range because of the frequency ofthe data formatted according to the predetermined network protocol andbecause of the type of encoding used.

[0154] Referring briefly back to FIG. 8 as noted above, this diagramillustrates a frequency spectrum of conventional network protocols, aswell as the exemplary network protocol according to the presentinvention. The inventors have discovered that the network protocolaccording to the present invention has a higher minimum occupiedfrequency, relative to the minimum occupied frequency of conventionalnetwork protocols such as SONET.

[0155] Dashed line 810 illustrates the lowest frequency that can beoccupied by the network protocol of the present invention as well as thepredetermined coding scheme. The inventors have discovered that GigabitEthernet protocol with 8B/10B encoding has a different lowest frequencyrelative the lowest frequency of a conventional network protocol such asSONET. The time constants of the present invention are adjusted toquickly achieve this lowest frequency of the network protocol of thepresent invention, which can comprise Gigabit Ethernet with 8B/10Bencoding.

[0156] Specifically, the time constant for the electrical circuits ofthe present invention is adjusted to make sure that the electricalcircuits have small enough time constants such that they do not trackdata at the lowest occupied frequency of the data. Otherwise, theseelectrical circuits could try to remove the low frequency components inthe data. In other words, distortion could be introduced into the datasignal, which would make it difficult to recover any data from thesignal.

[0157] The data frequency discussed in this specification andillustrated in FIG. 8 is defined as follows: when data passes through ahigh pass filter, the data may comprise a string of ones and zeros. Insituations where the data comprises a long sequence of zeroes (0s) orones (1s), such data achieves the lowest fundamental frequency of theprotocol used to format the data. Usually, the longer the string of likedata, such as all ones or all zeros, then the lower the data frequencythat is needed to be handled by a high pass filter circuit. For example,the conventional network protocol of SONET tests for a maximum number oflike characters in a row to comprise 77 bits. More consecutive like bitsthan this may exist, but this has been taken as a test maximum.

[0158] Opposite to the conventional network protocol of SONET, thenetwork protocol of the present invention that is encoded with apredetermined coding scheme, helps limit the number of consecutive onesand zeros between any two code groups of a data string. According to oneexemplary embodiment of the present invention, the coding schemecomprises 8B/10B encoding.

[0159] 8B/10B encoding allows large code spaces which in turn permits achoice of codes with an optimal number of ones and zeros. 8B/10Bencoding also limits the number of consecutive ones and zeros betweenany two code groups. 8B/10B encoding usually provides enough transitionsper code group to facilitate clock recovery. 8B/10B encoding also allowsthe use of special code words.

[0160] Specifically, every ten bit code group must fit into one of thefollowing three possibilities: (1) five ones and five zeros; (2) fourones and six zeros; and (3) six ones and four zeros.

[0161] 8B/10B encoding also includes the running disparity to helpmaintain DC balance and to provide additional error checking. Therunning disparity is understood by those skilled in the art. But as areview of this concept, by using the predetermined coding scheme of thepresent invention such as 8B/10B encoding, direct current (DC) balancingcan be achieved through the use of the running disparity. Runningdisparity is designed to keep the number of ones transmitted by atransmitter 530 substantially equal to the number of zeros transmittedby that transmitter 530. This should keep the DC level balance halfwaybetween the “one” voltage level “zero”.

[0162] Running disparity can take on one of two values: positive ornegative. In the absence of errors, the running disparity value ispositive if more ones have been transmitted than zeros, and the runningdisparity value is negative if more zeros have been transmitted thanones since power-on or reset. The 8B/10B encoding scheme is designed toprovide a high transition density which makes synchronization ofincoming bit stream easier for the receiver handling the data. Moredetails about the predetermined coding scheme of the present inventionthat comprises 8B/10B encoding is further described in U.S. Pat. No.4,665,517 issued on May 12, 1987, to Widmer, the contents of which, arehereby incorporated by reference.

[0163] 8B/10B encoding also provides that 8 bits of data are encoded to10 bits of transmitted code. The extra two bits of code can serve avariety of purposes, including differentiating control blocks from datablocks and providing DC balance and transitions for clock recovery.Although 8B/10B codes have previously been described because ofpopularity of 8 bit bytes, the 8B/10B encoding of the present inventionadditionally partitions each 8 bit byte into two sub-blocks which areseparately encoded. The result is that the 8B/10B is divided into a3B/4B coding and a 5B/6B coding.

[0164] Referring back again to FIG. 10, in light of the exemplarynetwork protocol and its predetermined coding scheme, it is desirable tohave the second time constant of the second high pass filter circuit1020 that comprises the third capacitor C3 and the equivalent resistanceof the first inductor L1 to be as low as possible. The equivalentresistance of the second high pass filter circuit 1020 comprises theimpedance of the first inductor L1 plus the output impedance of thesecond amplifier 1110 in parallel with impedance of the laser diode1100.

[0165] Those skilled in the art recognize that this impedance is not apure resistance, but the impedance may comprise a resistive componentand a reactive component, which works with the third capacitor C3 toform the high pass filter circuit 1020. The high pass filter circuit1020 can filter the data being coupled from the first amplifier 1010 tothe diode 1100.

[0166] The frequency response of the second high pass filter circuit1020 is governed by the time constant of the high pass filter circuit1020 comprising the third capacitor C3 and the equivalent resistance ofthe components discussed above. As is understood by those skilled in theart, the cut-off frequency (the frequency at which half the power ispassed to the third capacitor C3 and half is rejected) is provided bythe following equation:

f=1/(2πτ)

[0167] where τ=C₃R_(L)=time constant

[0168] Therefore, it is advantageous to keep the cutoff frequency of thethird capacitor C3 and the equivalent resistance of the high pass filtercircuit 1020 as high as possible (meaning that the time constant isreduced to as small value as possible) in order to allow the thirdcapacitor C3 to charge to the average value of the data as quickly aspossible at the start of a run-in interval 710 as illustrated in FIG. 7.The lower the time constant, the faster the high pass filter circuit1020 will settle and the faster the data transmission can begin.

[0169] The parameter that limits how high the second high pass filtertime constant can be low is the lowest frequency of the data signal—thecutoff frequency must be low enough to allow for the signal power tocouple through to the first diode 1100. The higher minimum frequency ofa Gigabit (or half Gigabit) Ethernet signal with 8B/10B encoding willallow the second high pass filter circuit 1020 to be set lower (wherethe capacitance value for the third capacitor is reduced). A lower timeconstant of the second high pass filter will allow it to settle faster.

[0170] Another component of the transition time intervals 610 cancomprise the power leveling circuit 910. The laser transmitter 905 cansettle faster at the beginning of a data transmission if the value ofthe fourth capacitor C4 is lower. However, the fourth capacitor C4 ofthe power level circuit 910 must be high enough that low frequency datadoes not cause the power level circuit 910 to change with the data beingtransmitted. That is, the power leveling circuit 910 must not change theoperating point of the laser diode 1100 as a function of frequency ofthe data. If the data has higher minimum frequency as shown for theexemplary Gigabit Ethernet with 8B/10B encoding data, then the fourthcapacitor C4 may be made smaller so that the power leveling 910 cansettle faster at the start of transmission of another subscriber opticalinterface 120.

[0171] The present invention demonstrates that the speed with which thetransmitter 530 can start is related to the minimum frequency occupiedby the data signal being propagated by transmitter 530. As the minimumfrequency is increased, the transmitter may be made to start faster.

Exemplary Optical Receiver Designed for Data Frequency of PredeterminedProtocol

[0172] Referring now to FIG. 12, this Figure illustrates a functionalblock diagram for an exemplary optical receiver 370 of the presentinvention. The optical receiver 370 can be designed to receive upstreamoptical data signals propagated according to a predetermined networkprotocol and with a predetermined timing scheme and coding scheme. Theoutput of the optical receiver 370 is upstream electrical data signalspropagated according to predetermined network protocols, or thepredetermined encoding scheme, as well as a predetermined timing scheme.

[0173] The optical receiver 370 can comprise an optical detector circuit1210. The optical receiver 370 may fully comprise an automatic gaincontrol circuit 390 and a limiting/conversion circuit that converts theupstream optical data signal 1200 into an upstream electrical datasignal 1205.

[0174] Referring to FIG. 13, this Figure illustrates exemplary circuitelement details corresponding to the function blocks above with respectto the optical detector circuit 1210, the automatic gain control 1215,and the limiting/conversion circuit 1220. The present invention is notlimited to the discrete circuit elements illustrated in FIG. 13 for theoptical receiver 370. Other different circuit elements or additionalcircuit elements that are described in each of the circuits describedbelow are not beyond the scope or spirit of the present invention.

[0175] The optical detector circuit 1210 can comprise a receiver diode1300 and a resistor 1305. The optical detector circuit 1210 may furthercomprise a transimpedance amplifier (TIA). The TIA of the opticaldetector circuit 1210 comprises a special amplifier that can convert alow impedance signal to a higher impedance signal. The data signal fromthe transimpedance amplifier 1310 can be capacitively coupled via thefirst capacitor 1330 to the limiting amplifier 1325 in order to removeany direct current (DC) bias.

[0176] A control line 1350 causes the gain of amplifier 1310 to changesuch that the output of amplifier 1310 is constant regardless of theinput level of the optical signal. The control is accomplished bydetecting the output level in diode 1315, storing that output levelanalog on the capacitor 1355 between 1315 cathode and ground. The outputlevel is compared against a reference on the non inverting input ofamplifier 1320, and the output level of 1320 is changed until the outputlevel from 1310 is such that the voltage on the capacitor 1355 is equalto the reference voltage on the non-inverting input.

[0177] The optical detector circuit may also include an automatic gaincontrol circuit 1215 may further comprise the buffer amplifier 1320 thatcompares the received voltage with a reference that represents a voltagebeing inputted into the linear amplifier 1320. And, if there is adifference between the measured voltage and the voltage supplied, theoutput of the buffer amplifier 1320 changes and feeds back into thesignal amplifier which may comprise a gain control circuit internal toit and its gain depends on the voltage that is coming in on thatparticular pin. The automatic gain control circuit 1215 may assist thelimiting/conversion circuit 1220 to operate at a constant amplituderegardless of variations in the input data signal level, thus increasingthe dynamic range of the receiver 370.

[0178] The limiting or conversion circuit 1220 may comprise a limitingamplifier 1325. The limiting amplifier 1325 can take a rough ordistorted data signal originating out of the optical wave guide andshape it or convert it into a nice set of binary data. The limitingamplifier 1325 of the limiting/conversion circuit 1220 can limit thesignal amplitude, converting the analog signal into a digital signal, aswell as converting the data signal into balanced data transmission. Asknown to those skilled in the art, balanced data transmission is atechnique of using two wires without a ground to couple a signal fromone circuit component to another.

[0179] In order to process data quickly, the capacitor 1330 needs to becharged to its average level as soon as possible. However, as notedabove, the charging of capacitor 1330 cannot be achieved too quickly,otherwise, the capacitor 1330 may introduce distortion of low frequencycomponents of the data, resulting in errors in data recovery. Therefore,it is desirable to set the capacitance of the capacitors of the opticalreceiver 370 as low as possible in order to quickly stamp out oreliminate any transients when switching from one transmitter 530 toanother. But, the capacitive values should not be so low that they starttrying to eliminate some of the data being received by the opticalreceiver 370.

[0180] The limiting or conversion circuit 1220 further comprises asecond capacitor 1335 and a third capacitor 1340. These second and thirdcapacitors 1335, 1340 can also be optimized with the present inventionby specifically adjusting these capacitors to handle data formatted to apredetermined network protocol, encoded with a predetermined codingscheme, and according to a predetermined timing scheme such as TDMA.

[0181] When a new transmitter 530 begins transmitting, and after it hassettled to its operating point, the operating point of the opticalreceiver 370 will need to change as well. This is because the poweroutput of two transmitters 530 can be different, and also because duringthe transition time during which one transmitter is shutting down andthe next transmitter 530 is starting up, the received signal power willbe changing, disrupting the quiescent operating point of the receiver370. Furthermore, it is not always the case that any transmitter wassending data just prior to the time another transmitter 530 switches on.

[0182] The voltage across capacitor 1330 will be changing during thistransition, and until capacitor 1330 can charge to the voltage requiredby the operating point of the ON transmitter, the receiver may not putout proper data. As was argued above for the transmitter, if thecapacitor 1330—resistor 1345 time constant is shorter, capacitor 1330can charge faster, and the receiver can put out valid data faster aftera new transmitter comes on. A smaller capacitor 1330—resistor 1345 timeconstant again requires that the lowest frequency occupied by the data,be higher, again working to the good of Gigabit Ethernet with 8B/10Bencoding.

[0183] In addition, if automatic gain control (AGC) is supplied, thoseskilled in the art know that the AGC has a time constant associated withit, that is related to the lowest frequency of data. If the AGC timeconstant can be lowered, the AGC will set itself to the value requiredby the new signal faster, so again data can be delivered faster.

Exemplary Processes for Increasing Efficiency of Upstream OpticalCommunications

[0184] Referring now to FIG. 14, this figure illustrates an exemplaryprocess 1400 for increasing upstream communication speed in an opticalnetwork from the vantage point of an optical transmitter. In otherwords, FIG. 14 illustrates an overview of the steps taken by an opticaltransmitter according to an exemplary embodiment of the presentinvention.

[0185] The description of the flow charts in the this detaileddescription are represented largely in terms of processes and symbolicrepresentations of operations by conventional computer components,including a processing unit (a processor), memory storage devices,connected display devices, and input devices. Furthermore, theseprocesses and operations may utilize conventional discrete hardwarecomponents or other computer components in a heterogeneous distributedcomputing environment, including remote file servers, computer servers,and memory storage devices. Each of these conventional distributedcomputing components can be accessible by the processor via acommunication network.

[0186] The processes and operations performed below may include themanipulation of signals by a processor and the maintenance of thesesignals within data structures resident in one or more memory storagedevices. For the purposes of this discussion, a process is generallyconceived to be a sequence of computer-executed steps leading to adesired result. These steps usually require physical manipulations ofphysical quantities.

[0187] Usually, though not necessarily, these quantities take the formof electrical, magnetic, or optical signals capable of being stored,transferred, combined, compared, or otherwise manipulated. It isconvention for those skilled in the art to refer to representations ofthese signals as bits, bytes, words, information, elements, symbols,characters, numbers, points, data, entries, objects, images, files, orthe like. It should be kept in mind, however, that these and similarterms are associated with appropriate physical quantities for computeroperations, and that these terms are merely conventional labels appliedto physical quantities that exist within and during operation of thecomputer.

[0188] It should also be understood that manipulations within a computeror discrete hardware elements are often referred to in terms such ascreating, adding, calculating, comparing, moving, receiving,determining, identifying, populating, loading, executing, etc. that areoften associated with manual operations performed by a human operator.

[0189] In addition, it should be understood that the programs,processes, methods, etc. described herein are not related or limited toany particular computer or apparatus. Rather, various types of generalpurpose machines may be used with the following process in accordancewith the teachings described herein.

[0190] The present invention may comprise a computer program or hardwareor a combination thereof which embodies the functions described hereinand illustrated in the appended flow charts. However, it should beapparent that there could be many different ways of implementing theinvention in computer programming or hardware design, and the inventionshould not be construed as limited to any one set of computer programinstructions.

[0191] Further, a skilled programmer would be able to write such acomputer program or identify the appropriate hardware circuits toimplement the disclosed invention without difficulty based on the flowcharts and associated description in the application text, for example.Therefore, disclosure of a particular set of program code instructionsor detailed hardware devices is not considered necessary for an adequateunderstanding of how to make and use the invention. The inventivefunctionality of the claimed computer implemented processes will beexplained in more detail in the following description in conjunctionwith the remaining Figures illustrating other process flows.

[0192] Certain steps in the process described below must naturallyprecede others for the present invention to function as described.However, the present invention is not limited to the order of the stepsdescribed if such order or sequence does not alter the functionality ofthe present invention. That is, it is recognized that some steps may beperformed before or after other steps without departing from the scopeand spirit of the present invention. Also, it is recognized that somesteps may be combined or performed simultaneously without departing fromthe scope and spirit of the present invention.

[0193] Step 1405 is the first step in the process 1400 for increasingupstream communications speed. In step 1405, electrical data is receivedby the processor 550 in the subscriber optical interface 140. Thiselectrical data can be generated by any one of a number of sources suchas a computer, a telephone, a set top box, a fax machine or any othersimilar devices, with the signals from analog devices being converted todigital in a suitable circuit such as Telephone input/output 555. Theprocessor 550 in step 1410 formats the electrical data for upstreamtransmission according to an exemplary network protocol such as GigabitEthernet.

[0194] Next in step 1415, the processor 550 can further encode theelectrical data with a pre-determined coding scheme such as 8B/10Bencoding. However, other encoding schemes are not beyond the scope of inspirit of the present invention. Other coding schemes can include, butare not limited to, 16B/18B and 64B/66B encoding.

[0195] Next in routine 1420 the speed to remove direct current (dc)components in the serial data signal is increased by adjusting a timeconstant of a first portion of a driver circuit 900 according to afrequency of the data propagated according to the exemplary networkprotocol and with the predetermined encoding. Further details of routine1420 will be discussed below with respect to FIG. 15.

[0196] Next in routine 1425, the speed to convert the serial encodedelectrical data into the optical domain is increased by adjusting a timeconstant of a second portion of the driver circuit 900 according to afrequency of the data that is propagated according to the networkprotocol with the predetermined encoding. Further details of routine1425 will be discussed below with respect to FIG. 16.

[0197] Next, in routine 1430 the speed to power up the laser transmitter905 is increased by adjusting a time constant of a power level circuit910 according to the frequency of data propagated according to thenetwork protocol and with a predetermined encoding. Further detail ofroutine 1430 will be discussed below with respect to FIG. 17.

[0198] Subsequently, in step 1435, the encoded electrical data isconverted into the optical domain according to a predetermined timingscheme such as time division multiple access (TDMA). Next, in step 1440the upstream optical data is propagated towards a data service hub 110according to the predetermined timing scheme of step 1435. The process1400 is carried out by each subscriber optical interface 140 and in aserial manner meaning that each optical transmitter 530 is powered up oractivated according to its time slot in the predetermined timing scheme.

[0199] Referring now to FIG. 15, this figure is a logic flow diagramillustrating an exemplary sub-method for 1420 for increasing speed toremove dc components from the serial data. Step 1505 is the first stepin the sub-method 1420 for increasing speed to remove dc components fromthe serial data. In step 1405, a frequency of the data encoded accordingto the network protocol and predetermined encoding scheme is determined.

[0200] Next, in step 1510 a first time constant of a first high passfilter circuit 1000 is adjusted to correspond with the frequency of thedata encoded according to the network protocol and with thepredetermined encoding scheme. As noted above, the inventors havediscovered that the exemplary network protocol of Gigabit Ethernet withthe predetermined encoding scheme of 8B/10B encoding has a lowestoccupied frequency that is higher than the lowest occupied frequency ofconventional optical network protocols such as SONET.

[0201] This means that the time constant of the first high pass filtercircuit 1000 can be adjusted by manipulating the capacitance of thisparticular circuit. However, it is noted that the time constant can beadjusted in other ways if other circuit components are used instead ofthe ones illustrated in the Figures of the present application. For thediscrete circuit components illustrated in the first high pass filtercircuit 1000 of the present invention, the time constant can be loweredby reducing the value of the capacitance of this circuit. In step 1515,the process returns to routine 1425 of FIG. 14.

[0202] Referring now to FIG. 16, this figure is a logic flow diagramillustrating a sub-method 1425 for increasing speed to convert serialencoded data into the optical domain. Step 1605 is the first step of thesub-method 1425 in which the frequency of the data encoded according tothe network protocol and the predetermined encoding scheme isdetermined. Next, in step 1610, the second time constant of a secondhigh pass filter circuit 1020 is adjusted to correspond with thefrequency of data formatted according to the network protocol and thepredetermined encoding scheme.

[0203] Specifically, the lowest occupied frequency of the data isdetermined in this step 1610 and the time constant of this second highpass filter circuit 1020 is adjusted to correspond with this lowestoccupied frequency of the data. As noted above with respect to the firsthigh pass filter circuit, other discrete circuit components can be usedother than those illustrated in order to form the second high passfilter circuit 1020. For the discrete circuit components illustrated forthe second high pass filter circuit 1020, the time constant is adjustedby increasing the capacitance values of the capacitors in this circuit,which in turn, lowers the time constant of the circuit. In step 1615,the process returns to routine 1430 of FIG. 14.

[0204] Referring now to FIG. 17, this figure is a logic flow diagramillustrating a sub-method 1430 for increasing speed to power up thelaser transmitter 905. The first step of the sub-method 1430 is step1705 in which the frequency of the data formatted according to thenetwork protocol and that is encoded according to the predeterminedencoding scheme is determined. In step 1710, a third time constant of apower level circuit 910 is adjusted to correspond with the frequency ofthe data formatted according to the protocol and encoded with thepredetermined encoding scheme.

[0205] Specifically, the time constant of the power level circuit 910can be lowered to correspond with the lowest occupied frequency of thedata that is formatted with the exemplary Gigabit Ethernet that isencoded with 8B/10B encoding. When other network protocols and codingschemes that are different from the ones described in the presentspecification are used, then the time constant can be adjustedaccordingly with such network protocols and encoding schemes. For theexemplary network protocol and exemplary predetermined encoding schemeof the present invention, the time constant of the power level circuit910 is typically lowered by adjusting the capacitance of a portion ofthe circuit. Specifically, the capacitance for the circuits is usuallyincreased.

[0206] As noted above, circuit components other than those illustratedin the drawings and discussed in the present specification can be usedwithout departing from the scope and spirit of the present invention.When circuit components other than those illustrated are employed, thesevalues can also be adjusted to manipulate the time constant of the powerlevel circuit 910. In step 1715, the process returns to step 1435 ofFIG. 14.

[0207] Referring now to FIG. 18, this Figure is a logic flow diagramillustrating an exemplary process 1800 for increasing upstreamcommunication speed in an optical network. Step 1805 is the first stepin the process 1800 for increasing upstream communication speed in anoptical network. In step 1805, optical data formatted according to apredetermined network protocol and encoded according to a predeterminedencoding scheme and transmitted according to a predetermined timingscheme is received by an optical receiver 370.

[0208] Specifically, an optical detector circuit 1210 can receive theoptical data formatted according to the network protocol, encoded withthe predetermined encoding scheme here, and according to a predeterminedtiming scheme. As noted above, according to one exemplary embodiment ofthe present invention, the network protocol can comprise GigabitEthernet while the predetermined encoding scheme can comprise 8B/10Bencoding. Further, the predetermined timing scheme can comprise timedivision multiple access (TDMA). However, other predetermined networkprotocols, predetermined encoding schemes, and predetermined timingschemes are not beyond the scope and spirit of the present invention.For example, other network protocols can include, but are not limitedto, Fiber Distributed Data Interface (FDDI) and Digital VideoBroadcasting-Asynchronous Serial Interface (DVB-ASI). Other encodingschemes can include, but are not limited to, 16B/18B and 64B/66Bencoding. Meanwhile, other data transmit timing schemes can include, butare not limited to, time division multiplexing (TDM) or code divisionmultiple access (CDMA).

[0209] In routine 1810, the speed in which an optical detector circuit1210 can receive optical signals is increased by adjusting a first timeconstant of the circuit. Further details of routine 1810 will bediscussed below with respect to FIG. 19. In routine 1815, the speed inwhich a detecting circuit 1210 can adjust between receiving differentsignals can be increased by adjusting a second time constant of anautomatic gain control circuit 1215. Further details of routine 1815will be discussed below with respect to FIG. 20.

[0210] In routine 1820, the speed in which a limiting or conversioncircuit 1220 that can receive and convert electrical data to opticaldata is increased by adjusting a third time constant of thelimiting/conversion circuit 1220. Further details of routine 1820 willbe discussed below with respect to FIG. 21. And lastly, in step 1825,the encoded optical data transmitted according to a predetermined timingscheme is converted into electrical data by the limiting/conversioncircuit 1220.

[0211] Referring now to FIG. 19, this figure is an exemplary logic flowdiagram illustrating the sub-method 1810 for increasing speed to receiveupstream optical data signals. Step 1905 is the first step of thesub-method 1810 in which the frequency of the data formatted accordingto the predetermined network protocol, predetermined encoding scheme,and predetermined timing scheme is determined. Next, in step 1910, thefirst time constant of a photo detector circuit 1210 is adjusted tocorrespond with the frequency of the data formatted according to thepredetermined network protocol, predetermined encoding scheme, andpredetermined timing scheme.

[0212] Specifically, the optical detector circuit 1210 is adjusted tohandle the lowest occupied frequency of the data formatted according tothe predetermined network protocol, and encoded according to thepredetermined encoding scheme and transmitted according to thepredetermined timing scheme. For the exemplary network protocol,exemplary encoding scheme, and exemplary timing scheme mentioned above,the time constant of the optical detector circuit 1210 can be lowered bylowering the capacitance values of the circuit.

[0213] However, as noted above, circuit components other than thoseillustrated in the figures can be used to form the optical detectorcircuit 1210. In such cases, the time constant can be adjusted bychanging the values of these other circuit components. Also, the timeconstant of the optical detector circuit 1210 can be increased dependingupon the predetermined network protocol, predetermined encoding scheme,and predetermined timing scheme employed. In step 1915, the processreturns to routine 1815 of FIG. 18.

[0214] Referring now to FIG. 20, this figure illustrates an exemplarysub-method 1815 for increasing the speed to adjust gain between opticaldata signals. The first step of sub-method 1815 is step 2005 in whichthe frequency of the data formatted according to the predeterminednetwork protocol, predetermined encoding scheme, and predeterminedtiming scheme is determined. In step 2010 the second time constant of again control circuit 1215 is adjusted to correspond with the frequencyof the data that is formatted according to the predetermined networkprotocol, predetermined encoding scheme, and predetermined timingscheme.

[0215] Specifically, for the predetermined network protocol,predetermined encoding scheme, and predetermined timing scheme for thepresent invention, the time constant of the gain control circuit 1215 islowered by increasing the capacitance values of that circuit. However,if circuit components other than those illustrated for the automaticgain control 1215 are employed, then the values of these other circuitcomponents could be adjusted in order to change the time constantthereof. Further, if a network protocol, a predetermined encodingscheme, and a predetermined timing scheme other than those mentioned areemployed, then the time constant could be raised or lowered dependingupon the lowest occupied frequency of the data with such protocols,encoding schemes, and timing schemes. In step 2015, the process returnsto routine 1820 of FIG. 18.

[0216] Referring now to FIG. 21, this Figure is a logic flow diagramillustrating an exemplary sub-method 1820 for increasing the speed toconvert optical data signals to electrical data signals. Step 2105 isthe first step in the sub-method 1820 in which the frequency of the dataformatted according to the predetermined network protocol, predeterminedencoding scheme, and predetermined timing scheme is determined. In step2110, a third time constant of the limiting conversion circuit 1220 isadjusted to correspond with the frequency of the data that is formattedaccording to the predetermined network protocol, predetermined encodingscheme, and predetermined timing scheme.

[0217] And as mentioned above, if circuit components other than thoseillustrated for the exemplary limiting/conversion circuit 1220 are used,then the values of these other circuit components can be adjusted tomanipulate the time constant thereof. And if other network protocols,encoding schemes, and timing schemes are used, then the time constantmay be lowered or increased depending upon the lowest occupied frequencyof the data formatted according to these protocols and schemes. In step2115, the process returns to step 1825 of FIG. 18.

[0218] The predetermined network protocol comprising Gigabit Ethernetand the predetermined encoding scheme comprising 8B/10B encoding allowsthe present invention to increase the transmission speed of upstreamoptical communications when a predetermined timing scheme such as timedivision multiple access is used in the optical network. As mentionedabove, Gigabit Ethernet with 8B/10B encoding comprises a higher minimumoccupied frequency for a given transmission rate compared to that ofother conventional optical network protocols such as SONET. With thehigher minimum occupied frequency, this allows a transmitter and areceiver to be constructed with lower time constants and resulting insignificantly increased speed in transitioning from one transmitter toanother when a predetermined timing scheme such as TDMA is employed bythe upstream optical communications.

[0219] It should be understood that the foregoing relates only toillustrate the embodiments of the present invention, and that numerouschanges may be made therein without departing from the scope and spiritof the invention as defined by the following claims.

What is claimed is:
 1. A method for increasing upstream communication inan optical network comprising the steps of: receiving serial electricaldata; formatting the serial electrical data with a network protocol;encoding the formatted data with a predetermined coding scheme forproviding adequate transitions per code group of the data to facilitateclock recovery; increasing a speed to remove direct current componentsfrom the serial data by adjusting a time constant of a first portion ofa driver circuit according to a predetermined frequency of the data thatis dependent upon the network protocol and encoding scheme; increasing aspeed to convert the serial encoded data in to the optical domain byadjusting a time constant of a second portion of the driver circuitaccording to the predetermined frequency; increasing a speed to power upan optical transmitter by adjusting a time constant of a power levelcircuit according to the predetermined frequency; and converting theencoded electrical data into optical data.
 2. The method of claim 1,wherein the step of formatting the electrical data comprises the step offormatting the electrical data according to a Gigabit Ethernet protocol.3. The method of claim 1, further comprising the step of propagating theoptical data in accordance with a predetermined timing scheme comprisingtime division multiple access (TDMA).
 4. The method of claim 1, whereinthe predetermined frequency of the data comprises an occupied frequencyof the protocol when the data comprises a maximum number of like bitspermitted by the protocol.
 5. The method of claim 1, wherein the step ofencoding the formatted data with a predetermined coding scheme comprisesencoding the formatted data in accordance with an 8B/10B coding scheme.6. The method of claim 1, wherein the step of increasing the speed toremove direct current (dc) components from the serial data comprisesadjusting a time constant of a high pass filter circuit of the drivercircuit.
 7. The method of claim 6, wherein the step of adjusting a timeconstant of a high pass filter circuit comprises lowering the timeconstant by decreasing capacitance of the high pass filter to correspondwith the predetermined frequency of the data.
 8. The method of claim 1,wherein the step of increasing the speed to convert the serial encodeddata in to the optical domain comprises adjusting a time constant of ahigh pass filter circuit of the driver circuit.
 9. The method of claim8, wherein the step of adjusting a time constant of the high pass filterof the driver circuit comprises lowering the time constant by decreasingcapacitance of the high pass filter circuit to correspond with thepredetermined frequency of the data.
 10. The method of claim 1, whereinthe step of increasing the speed to power up an optical transmittercomprises adjusting a time constant of a high pass filter circuit of thepower level circuit.
 11. The method of claim 10, wherein the step ofadjusting a time constant of a high pass filter circuit compriseslowering the time constant by decreasing capacitance of the high passfilter circuit to correspond with the predetermined frequency of thedata.
 12. A method for increasing upstream communication in an opticalnetwork comprising the steps of: receiving an optical signal that isformatted according to a network protocol and predetermined timingscheme and having a predetermined encoding; increasing a speed in whicha detecting circuit can receive optical signals by adjusting a timeconstant; increasing a speed in which the detecting circuit can adjustbetween different optical signals by adjusting a time constant;increasing a speed in which a limiting circuit can convert opticalsignals to electrical signals by adjusting a time constant; andconverting the optical signals to electrical signals.
 13. The method ofclaim 12, wherein the step of receiving optical signals comprisesreceiving optical signals formatted according to a Gigabit Ethernetstandard.
 14. The method of claim 12, wherein the step of receivingoptical signals comprises receiving optical signals encoded according to8B/10B encoding.
 15. The method of claim 12, wherein the step ofreceiving optical signals comprises receiving optical signals formattedaccording to a time division multiple access protocol.
 16. The method ofclaim 12, wherein the step of increasing a speed in which a detectingcircuit can receive optical signals comprises decreasing a time constantby decreasing capacitance of a photodetector circuit to correspond witha predetermined frequency of the data.
 17. The method of claim 12,wherein the step of increasing a speed in which the detecting circuitcan adjust between different optical signals comprises decreasing a timeconstant by decreasing capacitance of a gain control circuit tocorrespond with a predetermined frequency of the data.
 18. The method ofclaim 12, increasing a speed in which a limiting circuit can convertoptical signals to electrical signals comprises decreasing a timeconstant by decreasing capacitance of the limiting circuit to correspondwith a predetermined frequency of the data.
 19. An optical transmittercomprising: a driver circuit for receiving electrical data; a lasertransmitter for receiving data from the driver circuit and forconverting the electrical data into optical data that is transmittedaccording to a time division multiple access protocol; a power levelcircuit for supplying electrical energy to the laser transmitter; and aprocessor for controlling the driver circuit and the power level circuitin accordance with the time division multiple access protocol[SPW1 ].20. The optical transmitter of claim 19, wherein the laser transmitteris adjusted to handle a predetermined frequency of the data thatcomprises an occupied frequency of a Gigabit Ethernet protocol when thedata comprises a maximum number of like bits permitted by the protocol.21. The optical transmitter of claim 19, wherein the power level circuitis adjusted to handle a predetermined frequency of the data thatcomprises an occupied frequency of a Gigabit Ethernet protocol when thedata comprises a maximum number of like bits permitted by the protocol.22. The optical transmitter of claim 19, wherein the driver circuit isadjusted to handle a predetermined frequency of the data that comprisesan occupied frequency of a Gigabit Ethernet protocol when the datacomprises a maximum number of like bits permitted by the protocol. 23.An optical receiver comprising: a photodiode detector circuit forreceiving optical data transmitted according to a time division multipleaccess protocol; an automatic gain control circuit for adjusting a gainof the photodiode detector circuit; and a limiting circuit forconverting the received optical data into electrical data that istransmitted according to a time division multiple access (TDMA)protocol[SPW2 ].
 24. The optical receiver of claim 23, wherein thephotodiode circuit is adjusted to handle a predetermined frequency ofthe data that comprises an occupied frequency of a Gigabit Ethernetprotocol when the data comprises a maximum number of like bits permittedby the protocol.
 25. The optical receiver of claim 23, wherein theautomatic gain control is designed to a predetermined frequency of thedata that comprises an occupied frequency of a Gigabit Ethernet protocolwhen the data comprises a maximum number of like bits permitted by theprotocol.
 26. The optical receiver of claim 23, wherein the limitingcircuit is designed to a predetermined frequency of the data thatcomprises an occupied frequency of a Gigabit Ethernet protocol when thedata comprises a maximum number of like bits permitted by the protocol.27. An optical transmitter comprising: a driver circuit for receivingelectrical data; a laser transmitter for receiving data from the drivercircuit and for converting the electrical data into optical data that istransmitted according to network protocol other than SONET; a powerlevel circuit for supplying electrical energy to the laser transmitter;and a processor for controlling the driver circuit and the power levelcircuit in accordance with the time division multiple access protocol.28. The optical transmitter of claim 27, wherein the network protocolother than SONET comprises Gigabit Ethernet[spw3].
 29. The opticaltransmitter of claim 27, wherein the driver circuit, laser transmittercircuit, and power level circuit are designed to a predeterminedfrequency of the data that comprises an occupied frequency of a GigabitEthernet protocol when the data comprises a maximum number of like bitspermitted by the Gigabit Ethernet protocol.
 30. The optical transmitterof claim 29, wherein each circuit has a time constant that correspondswith the predetermined frequency.